The present invention relates generally to remotely controlled toy vehicles and, more particularly, to an improved communication system for controlling such toy vehicles.
Several types of communication systems are employed for remotely controlling the operation of toy vehicles. In one such communication system, control data packets are transmitted in a continuous stream by radio signals from a remote control device to the toy vehicle. Each data packet includes two types of bits, marker bits (W2) and data bits (W1). An example of a typical data packet employed in the prior art communication system is shown in FIG. 6. As illustrated in FIG. 6, the marker bits each have a 75% duty cycle and each marker bit is twice as long between rising edges as a data bit which has a 50% duty cycle. A single data packet includes four leading marker bits followed by a variable number of data bits with the number of data bits in a packet depending upon the control signal being transmitted. The data for controlling the operation of the toy vehicle is thus encoded in the number of data bits in a packet. For example, ten data bits in a packet may be an instruction for the vehicle to move forward, twenty-eight data bits in a packet may be an instruction for the vehicle to move forward and turn left, thirty-four data bits in a packet may be an instruction for the vehicle to move forward and turn right, and so. The width of each of the data bits is the same and the number of data bits used for each separate toy vehicle command signal is spaced at least six bits away from the number of data bits used for any other command signal to ease in decoding and to provide for packet level error checking. For example, a packet received with eleven data bits would be interpreted by the receiver/decoder in the toy vehicle to be an error.
While the data encoding schemes employed in such prior art communication systems are adequate for controlling toy vehicles with a limited number of controllable features, as the number of vehicle controllable features increases, the length of the packets required in such prior art encoding schemes becomes unacceptably long. For example, in using the above-described encoding scheme of the prior art in connection with a basic four-function vehicle controller, the longest transmitted command is 64 data bits long and when used with the four marker bits results in a total of 144 transmit elements (two transmit elements per bit). Since in the prior art encoding scheme each transmit element is about 315 microseconds in length, the longest packet for a four-function vehicle controller is approximately 45 milliseconds. Such a lengthy data packet is statistically more likely to be interrupted with intermittent radio noise then a shorter packet, particularly when the toy vehicle being controlled is at the distance limit of the communication range of the radio transmitter/receiver.
The prior art data encoding scheme in which a unique number of data bits is provided for each possible command is even less acceptable for controlling a toy vehicle in which a greater number of functions must be controlled. For example, newer toy vehicles include a seven position controller for steering functions, a seven position controller for drive functions and up to a three additional controlled functions (referred to as “twist”). The control of such a toy vehicle requires up to one-hundred forty-seven separate command codes (7×7×3) and, if implemented with the prior art encoding scheme having a separation of six data bits between commands, the longest command would be almost nine hundred data bits in length, taking more than 500 milliseconds to transmit. Such a lengthy command signal would unduly limit the responsiveness and range of such a toy vehicle to the point where the play value would be diminished.
In addition, the prior art encoding scheme does not have a “stop” command. Instead, the toy vehicle is programmed to stop in the absence of a command signal for a predetermined time period of about 50 milliseconds. Thus, when a user releases all of the control switches in order to stop the toy vehicle, no transmission is made by the controller and the toy vehicle continues in the then current direction of travel for at least an additional 50 milliseconds before actually stopping. The toy vehicle would also have to keep going for at least 50 milliseconds upon receipt of a noise signal because the receiver could not determine whether a stop command (no transmission) was desired.
The present invention provides a communication system having a data encoding scheme which overcomes many of the problems of the prior art encoding scheme, particularly, when used in connection with controlling a toy vehicle having a large number of controllable functions. With the present communication system, a data packet containing only 16 bits is employed for transmission of all control signals to the toy vehicle. In this manner, the time length of each data packet is minimized to improve responsiveness and reduce the likelihood of radio noise in the middle of the data transmission to increase range while still providing sufficient information to control multiple functions of the toy vehicle. Further, the encoding scheme employed in the present communication systems utilizes biphase encoded bits (50% duty cycle) to maximize reception distance with the bits being read at the middle of each transmit element thereby significantly decreasing the potential for decoding transient or erroneous data. In addition, with the present communication system, an affirmative, distinctive “stop” signal is transmitted by the remote control transmitted whenever the control switches are in the off position thereby providing enhanced and more rapid stopping of the toy vehicle and a higher immunity to reception errors then was possible with the prior art system. Finally, the present invention employs a digital phase-locked loop which looks for the middle of each transmit element to provide enhanced synchronization with a reduced likelihood of erroneous data being read. The present communication system provides shorter data packets, which results in short response times, a longer operational range and enhanced communication accuracy.